A Technique for High-Speed Microscopic Imaging of Dynamic Failure Events and Its Application to Shear Band Initiation in Polycarbonate
A Technique for High-Speed Microscopic Imaging of Dynamic Failure Events and Its Application to Shear Band Initiation in Polycarbonate
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动态失效事件的高速显微成像技术及其在聚碳酸酯剪切带引发中的应用
DOI：
10.1115/1.4053080
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Guduru, P. R.
中科院分区：
文献类型：
--
作者：
Malhotra, P.;Niu, S.;Srivastava, V.;Guduru, P. R.
报道了一种实验技术，它可以同时以高的空间和时间分辨率成像与动态失效事件相关的变形场。该技术的空间分辨率为1.1 μm，时间分辨率为250 ns，同时保持相对较大的视场（1.11 mm × 0.63 mm）。作为一个示范，该技术是用来成像的缺口尖端附近的变形场在聚碳酸酯的剪切不稳定性的开始。在缺口尖端附近的试样表面上沉积的直径为10 µm、间距为20 µm的有序散斑阵列有助于跟踪变形场的演变。实验结果表明，聚碳酸酯中剪切带（SB）的宽度在实验的分辨率范围内，在缺口尖端附近约为75 µm。测量还揭示了两个初始的本地化带附近的裂纹尖端，其中之一随后成为主导带，而另一个被抑制形成。实验的计算模拟进行了使用热机械耦合率相关的本构模型的聚碳酸酯，以获得进一步的洞察实验观察，使高的空间和时间分辨率的组合。模拟结果表明，合理的协议与实验观察到的运动场和功能附近的缺口尖端，同时也指出需要进一步完善的本构模型，在高应变率（105/s）校准，也占损伤演变。
An experimental technique is reported, which can image the deformation fields associated with dynamic failure events at high spatial and temporal resolutions simultaneously. The technique is demonstrated at a spatial resolution of ∼1 µm and a temporal resolution of 250 ns, while maintaining a relatively large field of view (≈1.11 mm × 0.63 mm). As a demonstration, the technique is used to image the deformation field near a notch tip during initiation of a shear instability in polycarbonate. An ordered array of 10 µm diameter speckles with 20 µm pitch, and deposited on the specimen surface near the notch tip helps track evolution of the deformation field. Experimental results show that the width of the shear band (SB) in polycarbonate is approximately 75 µm near the notch tip within resolution limits of the experiments. The measurements also reveal formation of two incipient localization bands near the crack tip, one of which subsequently becomes the dominant band while the other is suppressed. Computational simulation of the experiment was conducted using a thermomechanically coupled rate-dependent constitutive model of polycarbonate to gain further insight into the experimental observations enabled by the combination of high spatial and temporal resolutions. The simulation results show reasonable agreement with the experimentally observed kinematic field and features near the notch tip, while also pointing to the need for further refinement of constitutive models that are calibrated at high strain rates (∼105/s) and also account for damage evolution.